Improvements in early diagnosis and treatment for breast cancer in women have resulted in increased survivorship. An unintended consequence of increased survival, however, is that more women are living with the negative sequelae associated with cancer treatment, including decreased physical function. Exercise has been beneficial in arresting these sequelae, but adherence to exercise guidelines continues to be a challenge. As most breast cancer survivors are middle-aged and older, an alternative to enhance exercise engagement and adherence might be providing a low intensity exercise program. The overall purpose of this study is to assess the impact of a low intensity versus moderate intensity endurance exercise program on physical functioning on breast cancer survivors. It is hypothesized that participants of the low intensity exercise program will demonstrate similar physical functioning as participants in the moderate intensity exercise program. The Theory of Planned Behavior will serve as framework for the intervention. A convenience sample of 142 women, residents of Puerto Rico, age 50 or older, with a diagnosis of unilateral breast cancer, stage 0 thru II, who have received surgical treatment for breast cancer, with or without adjuvant therapy, will be randomly assigned to a low intensity or moderate intensity endurance intervention. Both interventions will be home-based, have a duration of 6 months, and be provided by physical therapists. An evaluator blinded to group assignment will assess participants at baseline and at completion of the intervention. Primary outcome measures will consist of physical functioning, and health-related quality of life.